Thread comparator



E. J. ALMQulsT THREAD COMPARATOR Filed March 3, 1942 UM y Patented Oct.19, 1943 THREAD COMPARATOR Ephraim J. Almqust, Winona, Minn.

Application March 3, 1942, Serial No. 433,144

1 Claim.

(Granted under the act of March 3, 1883, as amended April 30, 1928; 370O. G. 757) The invention described herein may be manufactured and usedby or for the Goverment for governmental purposes, without the paymentto me of any royalty thereon.

rlhis invention relates to a thread comparator.

An object o-f this invention is to provide a thread comparator havingspaced circular threaded portions thereon, preferably of the sameoutside diameter, with each portion having a different type of screwthread thereon.

Another object of this invention is to provide va compact, handy anduseful instrument for comparing some of the various types and surfaceconditions of threads which exist in the arts with standard types andsurface conditions of those threads on the instrument.

Another object of this invention is to provide a thread nish comparatorwhich may easily have inserted thereon duplicate replaceable samples.

Another object of this invention is to provide 'a thread finishcomparator which serves to compare the minute surface irregularities ofthreaded fabricated parts.

Another object of this invention is to provide a compact, handy anduseful instrument for comparing the appearance of fabricated screwthreaded portions with the appearance of standard threaded portions onthe instrument.

In particular, an object of this invention is to provide a compact,handy and useful instrument for comparing the nnish on fabricated screwthreaded portions with Vstandard finishes on threaded portions on theinstrument.

A finish comparator for smooth flat or smooth rounded surfaces isdisclosed in my copending application Serial No. 433,143 filed March 3,1942, which discloses a structure similar to that shown in the drawingin this application.

The instrument which is the subject of this invention is useful in thetesting and inspection of finished screw threads, but it is useful alsoto the designer and fabricator of the article upon which the screwthreads are placed. Besides being an instrument by means of which aparticular type of screw thread may be ascertained, the instrumentserves also as a qualitative standard for the particular type of screwthread under observation, i. e., the particular finish or surface of ascrew threaded portion on a fabricated article may be compared with thefinish or surface of the standard threaded portion on the instrument ininspection operation.

An instrument for comparing the surface conditions of flat and roundarticles is disclosed in my c-opending application.

The specific nature of the invention as well as other objects andadvantages thereof will clearly appear from a description of a preferredembodiment as shown in the accompanying drawingin which:

Fig. l is a plan view of a thread comparator which embodies my inventionand discloses fragmentary sections through the center of the comparator.

Fig. 2 is an end view taken substantially in the direction 2 2 on Fig.1.

Fig. 3 is an end view taken the direction 3 3 on Fig. l.

Fig. 4 is a section taken substantially on line 4 4 of Fig. 1.

Fig. 5 discloses a longitudinal section through a modified comparator.

In the particular embodiment of this inventi-o-n disclosed in thedrawing` three standard threaded portions on cylinders or specimensIlla, Ib, I0c are shown concentrically mounted on the axially extendingspindle II, but it is understood that spindle H may be made longerorsubstantially in shorter so as to accommodate more or fewer of thestandard threaded portions.

The threaded specimens or portions are spaced by means of spacers I2a,I2b which preferably have an outside diameter equal to the outsidediameter of the threaded specimens or portions and an inside diameterequal to the outside diameter of the spindle.

Spindle II has a reduced threaded portion IIa for a jam nut I3. Thethreaded portions or specimens Illa, Ich, loc and spacers I2a, I 2b areheld on the spindle between the jam nut I3 and split resilient ring I4which abuts against spindle shoulder IIb and tends to keep the threadedportions IIIa, lub, Ic and spacers I2a, I2b in Contact with one anotherby exerting a lock washer action on jam nut I3. Shoulder IIb may beconsidered to be a stop. Thus provision is made to prevent the jam nutfrom becoming loose and also to keep the threaded portions in contactwith one another when the instrument is subjected to large temperaturevariations.

The comparator may be assembled without the spring washer I4, if thespindle is turned down sufficiently to leave a shoulder for the specimenIc to abut against.

With screw threaded portions having approximately a '78" to 1%" outsidediameter, a suitable handy instrument may be made in which each threadedportion or specimen is approximately one and one-quarter inches inlength, but the exact length of the specimens may be conveniently madeshorter or longer than one and onequarter inches.

In an instrument which may be made in ac- Scordance with this inventionthe threaded portions Illa, lb, 10c may have the following types ofscrewthreadedportions thereon: '10m-outside diameter 7/g", Qthreads perinch fand of the NC or National coarse type; lllb, outside diameter FAW,14 threads per inch and of the NF :.or`

National fine type; Ic, outside diameter .ZV/3, 8 threads per inch andof the NA or Navy-Army type.

One end I Ic of the spindle ,Il has rolledlnurl.-

ing thereon to facilitate manual handling'of the instrument The threadedportions ma, |81), ,lc may `have various types of finish andsurfaceirrevgiilarties thereon and may be of such a standard 4that.screwthreads which have yacoarser lfini-sh Z onhave irrgularitiesthereon will be Arejected Yb'yan-inspector :wlien Ahe compares thefabricated screw @1i-raad Bilder inspection with the Corresponding:Medard @Grew threaded fportion on thefinsiw- 291:99??- It is obviousthat the threaded portions, speci- -gxgns or cylinders 40a, Mib, flc maybefeasily rexnoir/ed:byunscrewing lthe jam nut I3; v,other.lsirnilamspecimens or cylinders may be substituted for one or all ofthe specimens or cylindersyregnoved. This last featurefis' particularlyadvantag'eous since then specimens or cy1inders-which lliutfrom thesa-me 'piece of machined-stock may be placed on the spindle of one orvmorenof the instrumentsqlocated at diierent places in a manufacturingplant or at different localities. giince one large piece of machinedstock may be cut into a plurality of small vspecimensinavfimg:,thegsarne 4finish-successive--sz1ecimens of the .same

imay fbe easily inserted on the instrument constant overta period oftime. If -the specimens could not be replaced on the .comparatorvspindleVY"leasly, it 'would -be necessary -to immerse thefcom- 'paraitorfinioil.to prevent :tarnishing of the specirfki'lncLof tools ,with which .the w:k

estesa men surface and in that case the specimens would become polisheddue to the action of the inspector or user when he wipes the oil fromthe specimens on the comparator.

An alternate design is shown in Fig. 5. The spindle H is made tubularfor weight reduction purposes. The tubular end or handle of spindle'glio' Iis provided withan inside :thread and a threaded retaining plug'I=Id"-with a head having at least one at surface (not shown) forfacilitating assembly and disassembly with a wrench orlpliers.

Thefront end of the tubular spindle llc' has 'ian inner ltlnfeadedportion for the reception of one endof anlegrtension He whereby theeffective rlength of the spindle Il may be varied. Theopposite end ofthe extension lle is tubular and has `an inner screw thread for thereception ofscrew threaded retaining plug I3.

`Asalso mentioned in my above mentioned co- L.pending applicationthexmaterial .of Tthe suriace @nis/llamame@ s110111@ preferably Tee-ef:mesme ,material .as )the work .to 'gbe-compaigedyami machined'by thesame fmethod landivith the.,sarne iobefqeaipared is,processed. However,'experience -h s proven 'that the roughness .of a suniace ,can satisfac--torlilyfcemeared when 'the finish .Specimens-9,11 .thecomparatorfarelof dissimilar materiaglspjie. comparators of s* inless.for co "Q steel .can 1be .stati yactorily used for comparing surfacereuahnessfaf @aus image fram :ether kinds of steel, non., brass,loronzealurninurn, Zetc. l'lhis vniay". lce .done .principally ,by .triedieci method, lan'din ,mostcases byv the lvisual method as well, eventhough the .work is dotnein la .different manner ,and .with ,diilerent`tools were .used for ,the .surfaces ,of .the ,comparators v' 'I claim;

A thread comparator comprising a spindle having a bearing portion oruniformldiameter, a part 4of saidspin'dle ,forming -.a.'handle, Ya.thea'ded @r11-lider .remota-ily mounted on me bearing portion of thespindle, Eresilient ,means in abutting relation to .thehanldledpontionfor limiting the ',mvement .0f the .Cylinder with respect tothe.handle, and ,alarm-.nut on theend 0f' the Spindle .holding .said.Cylinder thereon.

@PERA-.IM .J. ALMQUISR

